Structure of genuine and conjugate Fermi holes and the first Hund rule in He-like systems

Abstract

The singly-excited states of He and He-like atomic ions in the manifold of the n = 3 principal shell have been studied replying on the full configuration interaction wave function focusing on the origin of the first Hund rule. The probability density distributions of the singlet-triplet pairs of states for the three orbital configurations of (1s)(3s), (1s)(3p), and (1s)(3d) have been examined in detail in the internal space (r1,r2,ϕ−). The structure of the genuine and conjugate Fermi holes for the (1s)(3s) and (1s)(3p) configurations has shown similar characteristics to those for the respective (1s)(2s) and (1s)(2p) configurations examined in an earlier study. A significantly smaller size of the genuine and conjugate Fermi holes for the (1s)(3d) singlet-triplet pair of states rationalizes the much smaller singlet-triplet energy gap of this pair than those for the (1s)(3s) and (1s)(3p) pairs of states.